Flexmark interferes with KaTeX code

[mtrevisan]

It seems that flexmark processes text inside KaTeX code, and I have to pre-process the text to add backslashes and removes
in order to render KaTeX correctly. What am I doing wrong?

The code I'm using is as simple as

private static Parser PARSER;
private static HtmlRenderer RENDERER;
static{
    MutableDataSet options = new MutableDataSet()
        .set(HtmlRenderer.SOFT_BREAK, "<br />\n");

    PARSER = Parser.builder(options)
        .build();
    RENDERER = HtmlRenderer.builder(options)
        .build();
}

and

Node document = PARSER.parse(content);
String html = RENDERER.render(document);

Please provide as much information about where the bug is located or what you were using:

• [X] Parser
• [ ] HtmlRenderer
• [ ] Formatter
• [ ] FlexmarkHtmlParser
• [ ] DocxRenderer
• [ ] PdfConverterExtension
• [ ] extension(s)

To reproduce the problem:

public static void main(String[] args){
    String input = """
$$
alpha[\%]
$$
        """;
    System.out.println(RENDERER.render(PARSER.parse(input)));
}

output:

<p>$$<br />
alpha[%]<br />
$$</p>

output expected:

<p>$$
alpha[\%]
$$</p>